The study proposes to identify, purify and determine the characteristics and site of action of a factor(s) in the sera of some gestational diabetic women noted in preliminary investigations in C57 mice to stimulate hyperglycemia and hyperinsulinism and pancreatic islet hypertrophy. The effects of the factor on mouse pancreas will be studied by light, immunofluorescent and electron microscopy. The presence and specificity of islet cell antibodies in pregnancy and postpartum sera of gestational diabetic women and the cord sera of their offspring will be determined. Placentae of gestational diabetic women will be examined for deposition of immune complexes and for pathologic changes characteristic of diabetic pregnancies.